The management of pressure ulcers poses a substantial burden to the healthcare system. Each year, the United States spends billions of dollars treating pressure ulcers and associated complications. Pressure ulcers are very common and they represent a significant source of morbidity and mortality for patients. The prevalence of pressure ulcers in the US alone is estimated to be between 1.5 and 3.0 million people, with two thirds of cases involving patients 70 or older.
Pressure ulcers, which are also known as pressure sores, bed sores, or decubitus ulcers, represent localized areas of tissue damage. Pressure ulcers often occur when the soft tissue between a bony prominence and an external surface is compressed for an extended period of time. Pressure ulcers can also occur from friction, such as by rubbing against a bed, cast, brace, or the like. Pressure ulcers commonly occur in immobilized patients who are confined to a bed, chair or wheelchair. Localized tissue ulceration results when pressure on the skin exceeds capillary filling pressure (approximately 32 mm Hg), which thereby impedes the micro-circulation in the skin and the underlying subcutaneous tissue. With compromised blood flow, the delivery of oxygen and nutrients to target tissues is impaired. If blood flow is not restored promptly, the skin and subcutaneous tissue will die and a pressure ulcer will develop.
Pressure ulcers will initially appear as areas of red or pink skin discoloration, but these areas can quickly develop into open wounds if left untreated. Open wounds can lead to severe health complications by exposing patients to life-threatening infections. The primary goal in the treatment and prevention of pressure ulcers is to relieve pressure on and around affected tissues. Pressure relief can be accomplished by frequently changing the position of immobilized patients and by using support surfaces that minimize surface pressure. Although pressure management is the most critical aspect of any successful treatment program, it is also important to ensure that patients receive adequate nutrition, engage in daily exercise, and follow a good skin care and personal hygiene protocol.
A Braden score is commonly used by caregivers to assess a patient's risk for developing a pressure ulcer. The Braden scale is composed of six criteria, which when taken together, can be used to estimate a patient's likelihood of ulceration and can also be used to determine the level of pressure ulcer prevention procedures required for a specific patient. The six components of the Braden scale are: sensory perception, moisture, activity, mobility, nutrition, and friction/shear forces. Each component is rated on a scale of 1 to 4, with the exception of friction/shear which is rated on a scale of 1 to 3. The maximum score is 23, and higher scores reflect a lower risk of developing pressure ulcers. In general, patients with a Braden score of less than 18 are considered to be at high-risk for developing a pressure ulcer.
Various devices and methods for treating and preventing pressure ulcers have been developed. The cornerstone of pressure ulcer prevention is to turn patients on a regular basis, such as every one or two hours. Patients confined to a wheelchair, chair, or other surface should be moved in such a manner. Intermittent relief of surface pressure has proven to be highly effective in preventing the development of pressure ulcers. However, various factors limit compliance with turning/repositioning protocols.
Alarm systems have been developed to help improve compliance with patient turning/repositioning protocols. Generally, these alarms are triggered when the system detects an inadequate amount of patient movement over a predefined time interval. Movement can be detected using various modalities, which include vibration sensors, pressure sensors, and video cameras. Although these systems can detect patient movement, they cannot reliably determine if the perceived movement resulted in adequate depressurization from specific regions of the body.
Also, current alarm systems cannot compute the cumulative pressure-time index (or pressure dose) at specific regions of the body. Although some alarm systems have been designed to measure the surface pressure distribution over a support surface, they are unable to directly correlate the measured pressure with discrete regions of a patient's body. For example, although a pressure sensitive mat placed under a patient can measure the overall surface pressure, it cannot automatically and directly measure the surface pressure at discrete regions of the body, nor can it directly track the cumulative pressure dose at specific regions of the body over time. Furthermore, pressure sensitive mats cannot easily and robustly distinguish between pressure resulting from patient contact with the support surface vs. pressure resulting from non-patient contact with support surface (i.e. books, food trays, etc.).
In addition to turning regimens, pressure ulcer prevention and management also commonly involves the use of pressure reducing support surfaces, which are well known in the art. Such support surfaces attempt to minimize the overall surface pressure and some support surfaces, such as alternating-pressure mattresses, are designed to modulate the surface pressure as a function of time. Although it is desirable to minimize the overall surface pressure, it is important to recognize that different regions of the body have different surface pressure thresholds.
For example, areas underlying bony prominences, such as the hips and sacrum, have relatively low surface pressure thresholds, which is why pressure ulcers commonly occur at these locations. Support surfaces are currently not able to detect or differentiate among specific regions of a patient's body. Without this detection ability, support surfaces are not able to selectively modulate surface pressure at specific regions of a patient's body. Also, current support surfaces cannot automatically identify areas of compromised tissue perfusion, so they are unable to automatically redistribute pressure away from ischemic areas.
There is a long-felt, definite and even urgent need for a system, method, and device that helps to prevent, detect, and/or treat pressure-induced ischemia and pressure ulcers by optimizing surface pressure at areas of compromised tissue perfusion. Various aspects of the present invention accomplish these objectives and substantially depart from the conventional concepts and designs of the prior art.